Re: [PATCH] net: sched: cls_u32: Avoid memcpy() false-positive warning

[Jamal Hadi Salim]

On Tue, Sep 27, 2022 at 11:37 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>
> To work around a misbehavior of the compiler's ability to see into
> composite flexible array structs (as detailed in the coming memcpy()
> hardening series[1]), use unsafe_memcpy(), as the sizing,
> bounds-checking, and allocation are all very tightly coupled here.
> This silences the false-positive reported by syzbot:
>
>   memcpy: detected field-spanning write (size 80) of single field "&n->sel" at net/sched/cls_u32.c:1043 (size 16)
>
> [1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@xxxxxxxxxxxx
>
> Cc: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Cong Wang <xiyou.wangcong@xxxxxxxxx>
> Cc: Jiri Pirko <jiri@xxxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> Reported-by: syzbot+a2c4601efc75848ba321@xxxxxxxxxxxxxxxxxxxxxxxxx
> Link: https://lore.kernel.org/lkml/000000000000a96c0b05e97f0444@xxxxxxxxxx/
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>

Reviewed-by: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>

cheers,
jamal